A capacitor (originally known as a condenser) is an electrical component used to store potential energy in an electrical field and is designed for enhance capacitance to a circuit of an electronic and electrical system, including power supply, digital frequency filter, signal filter, analog filter, resonate circuit, electric transmission system, and etc.
A large variety of different types of capacitors are available in the market. Physical forms and constructions of capacitors vary widely, and many types of capacitors are in common use. A capacitor usually has two conductors in a form of plate separated by a dielectric medium. The dielectric medium acts to increase charge capacity of the capacitor. When two conductors of a capacitor experience voltage difference, an electrical field is developed causing a net positive charge to collect on one conductor and a net negative charge to collect on the other conductor. Capacitance relates to the ratio of electric charges on the two conductors and potential difference between them. The capacitance of a capacitor is proportional to the surface area of the conductors and inversely to the gap between the two conductors.